OTTAWA - Prime Minister Stephen Harper adopted a more aggressive robocall defence Wednesday, dismissing suggestions his party was behind misleading and harassing calls to voters in the last federal election as nothing but "a smear campaign" by the opposition.

"The Conservative party can say absolutely, definitively, it has no role in any of this," Harper told the House of Commons on Wednesday.

For the third straight day, Harper faced a barrage of allegations in the Commons that Conservative operatives deliberately confused voters to suppress support for his opponents. But Harper added a new element to his counter-attack when he was challenged the NDP and Liberals to provide proof to Elections Canada that the Conservatives were behind the calls.

"The honourable leader of the NDP should provide her party's information to Elections Canada. Otherwise, I think we just conclude this is simply a smear campaign without any basis at all."

Elections Canada is investigating reports that voters in Guelph, Ont., received calls from a phone number with a 450 area code directing them to the wrong polling station. Phone records show the number behind the Guelph calls was the same one registered to "Pierre Poutine" of "Separatist Street" in Joliette, Que.

Elections Canada's chief investigator says in a sworn court document that the clearly fake name was likely used to cover the tracks of whoever was behind misleading and harassing calls to Guelph voters.

The phone records show the number registered to Pierre Poutine twice called Edmonton-based call centre RackNine Inc., on April 30 and May 1.

The records also show phones associated with Guelph Conservative candidate Marty Burke and the Guelph Conservative riding association made a total of 31 calls to RackNine between March 26 and early May.

The Burke campaign did not report any business with RackNine in its Elections Canada return. But the investigator says it is likely Burke's campaign had business dealings with RackNine.

"I think it is reasonable to believe that some sort of consumer relationship existed between the Marty Burke Conservative campaign in Guelph for the 41st general election and RackNine Inc., or between certain Burke campaign workers and RackNine Inc.," Mathews concludes.

"(And) that this relationship was related to the general election campaign in Guelph; and that the relationship related to the misleading calls made to Guelph area electors which they perceived as coming from the phone number 450-760-7746."

The claims, which have not been proven in court, are laid out in an Information to Obtain a Production Order filed in an Edmonton court in November.

RackNine has confirmed someone used its automated dialling service to make the diversionary calls. The company insists it did nothing wrong and that it is helping Elections Canada and the police in their investigation.

The Liberals and NDP say voters in dozens of ridings report getting misleading or harassing calls before the May 2 vote.

But Harper said most complaints only surfaced after the election, suggesting they come from sore losers.

"As I have become aware, apparently Elections Canada received virtually none of these complaints during the campaign outside of Guelph, but now it is receiving all of these complaints nine months after the election," he said during daily question period.

However, some complaints were filed before the May 2 vote.

David Bertschi, the Liberal candidate in Ottawa-Orleans, filed a complaint with Elections Canada in the midst of the election campaign, on April 19, 2011. Bertschi said the complaint detailed live, harassing calls received by about 35 voters in the riding.

"We complained before the election so the sore loser moniker doesn't apply," he said in an interview.

The callers purported to be calling on behalf of Bertschi's campaign but then aggressively questioned those who indicated they were inclined to vote Liberal. They would call back repeatedly on the same day, with each call becoming progressively more aggressive, Bertschi said.

He supplied Elections Canada with the names of those who'd received the calls. He said the agency got back to him asking for more evidence, including tape recordings of the calls, which he could not provide.

Later in the campaign, Bertschi said some Orleans voters also complained of receiving robocalls falsely advising them that the location of their polling stations had changed. He did not file a separate complaint with Elections Canada on those calls.

CBC News reported Wednesday that the Elections Canada investigation will involve interviews with some employees of a call centre based in Thunder Bay, Ont., operated by Responsive Marketing Group, a company hired by the Conservatives to reach out to voters.

According to the CBC report, an RMG worker who asked to remain anonymous said she was uncomfortable with the way she felt her fellow workers were asked to influence voters on behalf of the Conservative party. She alleged they weren't allowed to say they worked for a call centre, said the CBC report.

The employee said she and other workers took their concerns to the RCMP, CBC reported.

In a statement issued later on Wednesday, Responsive Marketing Group dismissed the allegations as "unsubstantiated speculation."

RMG said it employs the highest standards in the telemarketing industry and that it has not been contacted by Elections Canada, but will be contacting the agency to offer "full co-operation."

It says RMG callers were instructed to identify that they were calling on behalf of the Conservative party. It says it was contracted by the party to contact identified Conservative party supporters in ridings across Canada "to re-confirm their support, ensure they had correct voting location information, and encourage them to vote on Election Day."

Meanwhile, a Conservative Cabinet minister lashed out at the opposition over their allegations.

"For myself, I'm angry about that and our party takes its distance from these kinds of practices, this is unlawful, it's unacceptable and we condemn it."

Paradis says there's a difference between getting out the vote and suppressing voters from voting. He called the allegations troubling and said anyone found to be involved would no longer be welcome in the Conservative party.

Paradis says that the Conservatives are ready to collaborate with Elections Canada, the RCMP and whatever other institution probes the allegations.